1. Field of the Invention
The present invention relates to an optical device and a projector.
2. Description of Related Art
There has been known a three-plate projector having a color-separating optical system that separates a light beam irradiated by a light source into three color lights, three optical modulators that modulate the respective color lights in accordance with image information, a cross dichroic prism that combines the light beams modulated by the respective optical modulators (refer to, for example, Patent Document 1: Japanese Patent Laid-Open Publication No. 2000-221588, FIG. 5).
A polarization plate (optical conversion plate) that transmits only a light beam along a direction of a polarization axis out of the incident light beams and absorbs light beams along other directions so as to irradiate a predetermined polarized light is arranged on each of the incident side and the irradiation side of the optical modulator.
Such polarization plate has, e.g., a sapphire substrate with a high heat conductivity having a polarization film attached thereto, so that the heat generated due to the absorption of the light in the polarization film is radiated to the sapphire substrate.
According to the invention disclosed in Patent Document 1, however, since the polarization plate arranged on the downstream of the optical modulator is directly attached to the light-incident face of the cross dichroic prism, it is difficult that the heat conducted from the polarization film to the sapphire substrate is radiated to the outside.
To overcome such disadvantage, a following configuration might be suggested for example.
A prism support plate (base) for supporting a cross dichroic prism is made of heat-conductive material. The size of the sapphire substrate of the polarization plate is increased. Further, the sapphire substrate and the prism support plate are connected so that the heat conducted from the polarization film to the sapphire substrate is radiated to the prism support plate.
However, according to this configuration, since the size of the sapphire substrate should be increased, the cost of the optical device can not be reduced.
An object of the present invention is to provide an optical device and a projector capable of improving the heat radiation property of an optical conversion film at low cost.